feat: add /team skill — Agent Teams orchestrator for gstack

[HMAKT99]

You have 15 skills. You can only use one at a time.

Need security + risk + code review on the same PR? You run /cso, copy findings, run /risk, paste CSO output, run /review, synthesize everything. You are the message bus between your own tools.

What /team does

Spawns Claude Code Agent Teams where each teammate runs a gstack skill and they message each other directly:

You:   /team review

Claude: Spawning 4 teammates...

        "engineer"  → runs /review methodology
        "security"  → runs /cso methodology
        "risk"      → runs /risk methodology
        "perf"      → focuses on performance

        engineer: Found 3 issues (1 critical: race condition in checkout)
        security: Found 2 issues (1 high: missing auth on /api/admin)
        security → engineer: "Your race condition in checkout also has
                              a TOCTOU vulnerability — check line 47"
        risk: Bus factor=1 on payment_processor.rb
        perf: N+1 query on dashboard, 3x slower than last week

        UNIFIED FINDINGS (synthesized by lead):
        1. CRITICAL: Race condition + TOCTOU in checkout (engineer + security)
        2. HIGH: Missing auth on /api/admin (security)
        3. HIGH: Payment processor bus factor=1 (risk)
        ...

7 pre-built teams: ship, review, launch, incident, diligence, audit, custom. Requires CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 (user opts in).

Only .tmpl committed — bun run gen:skill-docs generates the rest.

Test plan

• .tmpl follows template pipeline
• Registered in gen-skill-docs.ts, skill-check.ts, test files